The orcs were first bred by the Dark Power of the North in the Elder
Days. It is said that they had no language of their own, but took what
they could of other toungues and perverted it to their own liking, yet
they made only brutal jargons, scarecely sufficient even for their own
needs, unless it were for curses and abuse.

This definition and along with some work by some linguists produced
after some time and hard work an actual dictionary of Black Speech terms.
You will find this dictionary online here for your use. The source where I
found the dictionary is provided in the sources section of this object.